Fossil Vertebrate of the Month: Epicyon haydeni

Last month, while measuring teeth in the collections of the University of Montana and Idaho State University, I came across jaws of one of the more impressive carnivores ever to have lived. The picture at left (from UM) may not do the size of the animal justice, but Epicyon haydeni is the most massive known canid; the largest known individuals may have exceeded 200 pounds, putting them well within the size range of modern black bears. Epicyon was a member of a group of canids known as borophagines that were among the most common carnivores of the North American Oligo-Miocene. Borophagines are often described as hyena-like, and many of the larger taxa - including Epicyon - were likely bone-crushing predators. However, the group was very diverse and many of its members, especially in the Oligocene and Early-Mid Miocene, were actually fairly small; at least one species had an almost raccoon-like morphology. In many Late Miocene faunas, two species of Epicyon co-occur: the larger E. haydeni and the smaller (but still very big) E. saevus. Canid experts extraordinaire Xiaoming Wang and Richard Tedford have suggested that this is the result of character displacement, making Epicyon an excellent example of how the fossil record can record ecological and evolutionary patterns.